The invention relates to a double-shaft forced-feed mixer for mixing materials in powder, grain and plastic form, for example for the production of building material mixtures or the like, comprising a mixing trough and in this mixing trough two mutually parallel, oppositely driven mixing shafts extending between mutually opposite end walls of the mixing trough and fitted with spirally arranged mixing tools especially following a helical line, with substantially horizontally directed rotation axes, the directions of rotation of the mixing shafts being selected so that the mixing tools run upwards between the mixing shafts, while the mixing tools of the individual mixing shafts are formed and arranged in such a way that they effect contrary directions of delivery along the individual mixing shafts, the mixer further comprising charging means for the introduction of granular and if necessary liquid mixture components into the mixing trough and a closable bottom emptying opening, especially as rotary slider closure, extending over a large part of the trough length and arranged in the mixing trough bottom between the two mixing shafts.
In mixing techniques hitherto two different mixers have been necessary for the two manners of operation of continuous mixing and mixing by batches, which mixers have separately their fixed fields of application. For greater throughputs--but with limited mixing quality--the continuously operating double-shaft throughflow mixer is used, for smaller throughputs but with high mixing quality the discontinuously working double-shaft batch mixer has been used.
While in their assembly the two mixing systems are similar, they differ distinctly in their manners of operation.